<!DOCTYPE html>
<html lang="en">

<head>
  <meta charset="UTF-8">
  <meta http-equiv="X-UA-Compatible" content="IE=edge">
  <meta name="viewport" content="width=device-width, initial-scale=1.0">
  <title>内部JavaScript</title>
</head>

<body>
  <div></div>

  
  <!-- 一般script标签写在body上 -->
  <script>
    alert('你好，JavaScript')
  </script>
  <!-- alert 出现警告弹窗 -->
</body>

</html>